Commits on Aug 25, 2022

1. Fix error handling when failing to install a deb package …

   The current error handling code for when a deb package fails to be
   installed currently has a chain of commands linked together by && and
   ends with `exit 1`. The assumption is that the commands would succeed,
   and the last `exit 1` would end it with a non-zero return code, thus
   fully failing the target and causing the build to stop because of bash's
   -e flag.
   
   However, if one of the commands prior to `exit 1` returns a non-zero
   return code, then bash won't actually treat it as a terminating error.
   From bash's man page:
   
   ```
   -e      Exit immediately if a pipeline (which may consist of a single simple
   	command), a list, or a compound command (see SHELL GRAMMAR above),
           exits with a non-zero status.  The shell does not exit if the
           command that fails is part of the  command  list  immediately
           following a while or until keyword, part of the test following the
           if or elif reserved words, part of any command executed in a && or
           || list except the command following the final && or ||, any
           command in a pipeline but the last, or if the command's return
           value is being inverted with !.  If a compound command other than a
           subshell returns a non-zero status because a command failed while
           -e was being ignored, the shell does not exit.
   ```
   
   The part `part of any command executed in a && or || list except the
   command following the final && or ||` says that if the failing command
   is not the `exit 1` that we have at the end, then bash doesn't treat it
   as an error and exit immediately. Additionally, since this is a compound
   command, but isn't in a subshell (subshell are marked by `(` and `)`,
   whereas `{` and `}` just tells bash to run the commands in the current
   environment), bash doesn't exist. The result of this is that in the
   deb-install target, if a package installation fails, it may be
   infinitely stuck in that while-loop.
   
   There are two fixes for this: change to using a subshell, or use `;`
   instead of `&&`. Using a subshell would, I think, require exporting any
   shell variables used in the subshell, so I chose to change the `&&` to
   `;`. In addition, at the start of the subshell, `set +e` is added in,
   which removes the exit-on-error handling of bash. This makes sure that
   all commands are run (the output of which may help for debugging) and
   that it still exits with 1, which will then fully fail the target.
   
   Signed-off-by: Saikrishna Arcot <sarcot@microsoft.com>

   

   saiarcot895 committed Aug 25, 2022
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